This research project is designed to further current knowledge of cognitive, social, and neurological processes that underlie the development of hierarchical manipulative and token-mediated communicative behavior in human and nonhuman primates. This goal will be accomplished by conducting in-depth, longitudinal comparative studies of tufted capuchin monkeys (Cebus apella), a primate species known for its anomalous combinatorial skills. Research by the Principal Investigator (PI) has shown that capuchin monkeys exhibit manipulative strategies analogous to those exhibited by great apes and human children. The PI now seeks to conduct additional research which will seek to examine the following four target areas: 1) Inter-animal communication; 2) generalization of communicative behavior; 3) inter-individual differences in the development of token-mediated communication; and 4) the relation between the use of tokens and the production and use of stone tools. We seek to broaden the skill set of our animals to include naming aspects of tokens and tools, use of a large set of tool sites, and sequential use of different type of tools for a single task (tool-combinations in order to test hypotheses concerning human-ape/monkey evolutionary continuity of combinatorial knowledge base generated through years of research utilizing capuchin monkeys as experimental subjects. In addition technologies and test procedures adapted from studies with great apes and humans will be developed further for use phase of this research. The present set of experiments will advance our understanding of evolutionary and developmental processes that underlie the manipulative and communicative capacities of primates, including modern humans, great apes, and their direct prehistoric predecessors.